1. Field of the Invention
The present invention relates to a separation and receiving apparatus for a spent nuclear fuel rod, and more particularly, to a separation and receiving apparatus for separating a hull and a pellet from a spent nuclear fuel rod, capable of effectively and automatically separating and receiving a hull and a pellet made of uranium oxide (UO2), while security and automation being guaranteed.
2. Description of the Related Art
Nuclear fuel is a material capable of producing energy by entering a nuclear reactor and causing a chain reaction of nuclear fission. Spent nuclear fuel is the material left after the nuclear fission. Generally, uranium 235 235U•uranium 233 233U•plutonium 239 239Pu and the like is a representative as material used for nuclear fuel. Uranium 235 235U is contained in only 0.7% of natural uranium. Accordingly, in the case of using natural uranium, the amount needed for reaching critical mass increases. Also, light water strongly absorbing neutrons may not be used as a moderator. Accordingly, the capacity of a nuclear reactor becomes large. Consequently, a lot of nuclear reactors use enriched uranium which artificially increases the ratio of uranium 235 235U as fuel material. In particular, a reactor for ship propulsion needing minimization or an electricity generating reactor limited by building cost per a certain output usually uses enriched uranium.
Nuclear generation is to slowly react the nuclear fuel in a reactor, generate thermal energy, and generate electricity by using the generated thermal energy. Nuclear generation uses nuclear fuel such as natural uranium that is enriched to between about 3 and 5%. When new fuel is added into a reactor, the fuel is burnt for about three periods to generate thermal energy. When one period is terminated, the reactor is stopped and a third of fuel is replaced. In this case, one period is about 18 months for which nuclear fuel is put in a reactor and generates energy through nuclear fission. When one period is over, equipment comprising a power plant such as a turbine or a steam turbine, a generator, all types of valves, a pump, etc. receive maintenance. When the maintenance is completed, the power plant is restarted and generates electricity for the next period, 18 months.
In this instance, nuclear fuel undergoes fission in a reactor in the form of being contained in a nuclear fuel rod. In this instance, the nuclear fuel rod is about 10 mm in diameter and about 4 m in length. A stable, corrosion-resistant zirconium alloy, for example Zircaloy, that is about 1 mm in width. Hull caps are provided on both sides of the hull to be capable of being sealed by resistance welding or the like.
Fuel manufactured in the form of a pellet is loaded into the hull of each nuclear fuel rod and tens to millions of nuclear fuel rods manufactured as above are used in a bundle for nuclear fuel used for nuclear power generation. According to a conventional method, spent nuclear fuel burnt in a nuclear power plant is stored in a tank without being processed. However, the longer the period of nuclear power generation, the more an amount of spent nuclear fuel accumulates. Consequently, a huge storage space is needed. Also, the necessity and dangerousness of disposing the accumulated nuclear wastes remains. In some countries, spent nuclear fuel rods are transferred to a permanent disposal area to be stored for the long term. On the other hand, nuclear fuel may be separated from the hull for recycling the spent nuclear fuel.
To recycle or to dispose of nuclear fuel, a nuclear fuel rod is dismembered to separate the nuclear fuel and the hull after the nuclear fuel is completely used in a reactor. However, in the case of separating nuclear fuel from a hull by using a current technology, nuclear fuel materials such as solid uranium, plutonium, or the like, nuclear fission products, and hull materials remain in the hull. The hull is classified as high-level radioactive waste. In particular, in the case of separating nuclear fuel from a hull by using wet processing, high-level radioactive waste such as a nuclear fuel a liquid cleaning solution and the like are spread on the inner surface and the outer surface of the hull. Accordingly, more special processing is needed.
Two methods are generally used for the management of spent nuclear fuel. One is a method of putting spent nuclear fuel in a rock bed in the ground to a depth of more than 500 meters and thoroughly isolating the spent nuclear fuel from the human ecosystem. This is known as permanent disposal. The other is a method of separating recyclable materials from spent nuclear fuel (this is referred to as ‘reprocessing’), reusing the separated nuclear fuel materials, and permanently disposing of high-level radioactive waste.
In particular, a spent nuclear fuel rod is cut to about 25 cm in length. The cut spent nuclear fuel rod is transferred to a disposal area such as a hot cell by a robot and a slitting operation for separating a pellet and a hull is performed. In this instance, a heating device is provided to supply the high heat of reaction to the inside of a vertical reactor in order to separate a hull and a fuel rod in the form of a pellet in the conventional method. In this instance, the heating device is in the shape of a cylinder wrapping the outside of the vertical reactor. Also, a vertical screw is provided in the vertical reactor and splits the hull through a complicated mechanical mechanism. Accordingly, it takes a long time to complete the operation.
Also, the complicated structure makes manufacturing difficult and increases manufacturing cost. Also, the manipulation of the complicated structure prolongs the operation time. Namely, since the introduction of automation processing becomes difficult and a handle or the like has to be manually manipulated, the operation efficiency decreases.
Also, it is difficult to secure the safety of the process because of a complicated driving method and complicated processing. Also, it is very inconvenient to separate a hull and a pellet contained in the same vessel.